sped up sim step by about 200%

Noticed that it was quite slow compared with things like action
sendwanted. Guessed that the slowdown is largely due to every step
doing a simulated git pull/push.

So, rather than always doing a pull/push, only do those when no actions
are found without doing a pull/push.

This does mean that step will sometimes experience a split brain
situation, but that seems like a good thing? Because step ought to
explore as many possible scenarios as it reasonably can.

doc/todo/git-annex_proxies.mdwn

@@ -120,11 +120,6 @@ present bar 9testfile
   clients having direct connections to the nodes, but not the same when
   there are more than 2 clients connected to the 2 gateways.
 
-* sim: Detect instability. This can be done by examining the history,
-  if a file is added or removed from the same repository repeatedly,
-  there is probably instability, although it may be an instability that
-  dampens out later.
-
 * sim: Set a random preferred content expression. Rather than generating a
   fully random expression, it would probably be most useful to take a set
   of terms and build an expression that randomly combines them with
@@ -140,12 +135,6 @@ present bar 9testfile
 
 ## items deferred until later for balanced preferred content and maxsize tracking
 
-* `git-annex assist --rebalance` of `balanced=foo:2` 
-  sometimes needs several runs to stabalize.
-
-  May not be a bug, needs reproducing and analysis.
-  Deferred for proving behavior of balanced preferred content stage.
-
 * The assistant is using NoLiveUpdate, but it should be posssible to plumb
   a LiveUpdate through it from preferred content checking to location log
   updating.

doc/todo/proving_preferred_content_behavior.mdwn

@@ -113,3 +113,5 @@ The location log history could be examined at the end of the simulation
 to find problems like instability.
 
 [[!tag projects/openneuro]]
+
+> [[done]], see `git-annex sim` command. --[[Joey]]